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Frequency Protection (ANSI 81)
155
7UM62 Manual
C53000-G1176-C149-3
Figure 2-73 shows the logic diagram for the frequency protection function.
Figure 2-73
Logic Diagram of the Frequency Protection
2.21.2 Setting Hints
General
The frequency protection will only be effective and accessible if address
has been set to
Enabled
during the configuration of the
protective functions. Set
Disabled
if the function is not required. Address
is used to switch the function
ON
or
OFF
, or to block only the trip
command (
Block Relay
).
Pick-Up Values
The nominal system frequency is programmed in Power System Data 1, and the
pickup settings for each of the frequency elements
to
determines whether the function will be used for overfrequency or underfrequency
protection. Set the pickup threshold lower than nominal frequency if the element is to
be used for underfrequency protection, and higher than nominal frequency if it is to be
used for overfrequency protection.
For the f4 frequency stage, the previously explained circumstances are only relevant
if the
parameter is set to
Automatic
(default setting). If
desired, this parameter can also be set to
f>
or
f<
, in which case the evaluation
direction (increase or decrease detection) can be specified independent of the
parameterized
threshold.
FNo. 05206...
FNo. 05236...
FNo. 05232...
&
U
123
f
OR
FNo. 05203
FNo. 05214
FNo. 05212
FNo. 05213
FNo. 05211
”1”
ON
OFF
Measurement/
Logic
U>Umin
OR
OR
Note:
If the element is not required, the frequency setting should be set equal to the nominal
frequency, in which case the element becomes inactive.